Lattice constants of GaAs layers grown by molecular beam epitaxy were examined by using the high resolution x-ray diffractometer. For highly doped samples ͑up to 9ϫ10 18 cm Ϫ3 of free-electron concentration͒ we observed an increase of the lattice constant with respect to the undoped layers. Since substitutional silicon atoms decrease the lattice constant of GaAs, the results are explained by the influence of free-electrons via the deformation potential of the ⌫ minimum of the conduction band. The best fit to our diffractometric data was obtained for the band-gap deformation potential equal to Ϫ8.5 eV.
Electron tunneling from InAs∕GaAs quantum dots has been studied by deep level transient spectroscopy (DLTS). Comparing DLTS data with theory, we demonstrate how the results can be interpreted for situations where the emission mechanism is pure tunneling. An illusory anomalous tunneling dependence on electric field is resolved by taking into account the energy level distribution originating from size fluctuations in the quantum dot ensemble.
By measuring the thermal emission rates of electrons from InAs∕GaAs quantum dots, capture cross sections in the extremely high region of 10−11–10−10cm2 have been found. These data have been confirmed by using an additional method based on a static measurement at thermal equilibrium, where the Fermi level is positioned at the free energy level of the quantum dot s shell.
Structural and photoluminescence (PL) properties of Si implanted with hydrogen, Si : H (at hydrogen doses ≤ 4 × 10 16 cm −2 and ion energy E ≤ 135 keV) and subjected to heat treatments up to 1320 K under hydrostatic Ar pressure up to 1.2 GPa were investigated. The structure of the temperature−pressure treated Si : H exhibits similarities to the structure of porous silicon. Visible PL at about 400−440 nm detected for Si : H treated at 720 K/920 K and 1.2 GPa is related to the presence of hydrogen and oxygen atoms in the implanted region of Si : H.
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